The invention relates to a remote control residential and commercial circuit breaker providing overload current protection and load management.
Circuit breakers provide overcurrent protection for preventing personal injury and property damage. A loadcenter or panelboard receives electrical power from the utility company transformer and routes the electrical power through a main circuit breaker and then through branch circuit breakers to designated branch circuits, each supplying current to one or more electrical loads. The circuit breakers are designed to interrupt the electrical current if it is excessive or outside the design limits of the conductor and loads, to reduce the risk of injury and damage. Branch circuit breakers are provided in narrow width molded cases which fit into designated slots or pole openings in the panelboard. The two most common widths for such circuit breakers are one inch and three-quarter inch, which is the outside width dimension of the molded case.
A circuit breaker has a thermal/magnetic trip characteristic. The thermal characteristic is operative in response to overload current of extended duration which heats a bimetal member, causing movement of the latter, which in turn releases a latch to trip open a set of contacts. For example, the thermal characteristic would respond to 30 amps being drawn in a 15 amp circuit. The magnetic characteristic is operative in response to a sudden high magnitude current overload condition, and uses the magnetic field generated in a magnetic core to attract an armature, which movement releases the latch to open the contacts. As an example, the magnetic type actuation occurs in response to a short circuit wherein the hot line conductor becomes directly connected with ground or neutral, bypassing the load.
It is known in the prior art to provide remote controlled circuit breakers wherein the breaker contacts are tripped to an open condition by an actuator responding to a control signal. This enables the circuit breaker to additionally perform a switching function and manage a load connected to the breaker, such that the breaker performs the dual functions of overload current protection and load management. A disadvantage of using the breaker contacts to perform a switching relay type function is that the breaker contacts are designed to be able to interrupt high current, not for repeated operation.
The present invention provides a circuit breaker with a first set of contacts provided by a pair of separable overload breaker contacts for overload current protection, and a second set of contacts provided by a pair of switching relay contacts having open and closed conditions and electrically connected in series with the overload breaker contacts and providing load management. Trip structure causes separation of the overload breaker contacts in response to overload currents therethrough. An actuator is energizable to mechanically actuate the switching relay contacts.
In one aspect of the invention, feedback circuitry responsive to the actuator provides status indication of the condition of the switching relay contacts, and in turn the managed load.
In another aspect, the noted structure is provided in a common case, and concurrent heating of the case by both the overload current trip structure and a solenoid actuator is prevented. Only one or the other of such trip structure and such solenoid is allowed to heat the case.
In another aspect, structure is provided enabling packaging within a narrow case of standard width of one inch or less. A negative gradient acting spring and particular orientation reduces the holding requirements of an actuating solenoid for the switching relay contacts, which reduced holding requirements enables use of a small solenoid, facilitating the noted packaging. In a further aspect, magnetic flux coupling structure is provided adjacent a movable contact arm of the switching relay contacts and provides a hold down electromagnet holding the switching relay contacts in the closed condition in response to overload currents therethrough such that the switching relay contacts remain closed and resist blow-apart force, and instead the circuit is interrupted by the overload breaker contacts in response to the overload current. The magnetic flux coupling structure providing the hold down electromagnet urges the switching relay contacts to the closed condition with increasing force with increasing current flow therethrough, which in turn reduces the holding requirements of the noted negative gradient acting biasing spring under overload current conditions, which in turn further reduces the holding requirements and size of the actuating solenoid, further facilitating the noted packaging.